In many environments, it is desirable to deliver or mix materials in relatively precise amounts. For example, in hospitals and pharmacies, syringes, medical containers, or other receptacles are routinely filled with precise amounts of parenteral fluids. In these and other areas, the performance of the material delivery system is measured in terms of its speed, accuracy, and reliability.
The speed, accuracy and reliability of conventional material delivery systems are dependent upon the particular performance characteristics of the associated pumping mechanisms, if any; the particular physical characteristics of the pathways which convey the material; and the nature of the material itself.
For example, in the case of conventional peristaltic pumping mechanism, which are in widespread use, the desired physical characteristics and tolerances of the tubing segments associated with the pump rotors can be initially controlled by following careful manufacturing methods. However, once in use, the dimensions and other physical characteristics of the tubing segments are subject to change; for example, due to repeated expansion and contraction by the peristaltic pump rotors or by temperature changes. These changes can introduce metering errors which are either random or change with time.
Furthermore, even though a given peristaltic pump may also provide consistently accurate and reliable service when used to convey a particular material through a tubing segment of given physical characteristics, its accuracy and reliability can significantly change if a tubing segment having different physical characteristics is substituted, or if a material having different flow characteristics is conveyed.
It is an object of this invention to provide a flow control method and device for a material delivery system, the method and device having a consistently high degree of speed, accuracy, and reliability, independent of the particular physical characteristics of the associated delivery system and any changes which may therein occur.